JPS5996485A - Control method for electrification of glow plug - Google Patents

Abstract

PURPOSE:To control an effective voltage, applied on a glow plug, so that it is made uniform indepenently of variation in a power supply voltage, by a method wherein a signal proportinal to the square of a voltage is averaged in DC form, and electrification is effected through comparision of the mean value with a specified comparison voltage. CONSTITUTION:When square wave intermittent electrical connection is made on a glow plug, a power PON during electrical connection is proportional to the square of a voltage VON during electrical connection, and thereby the mean power equivalent to an intermittent period is made uniform even if the VON is varied. Thereby, a voltage proprtional to the square of the VON is produced that the average of a time equivalent to an intermittent period is found and the mean value Vm is made uniform independently on the VON. For this purpose, by means of a circuit consisting of a Zener diode 30 and a resistor 31, a source voltage is controlled so that it is set to approximate square within a practical range, and based on the value, switching is effected. This produces an approximately constant effective voltage, and causes the temperature of a glow plug to be made approximately constant independently of a source voltage.

Description

[Detailed description of the invention] The present invention applies a voltage higher than the rated voltage to rapidly heat the
The present invention relates to a method for controlling energization of a glow plug in which stable heating is performed by switching the voltage to (1) intermittent energization after the temperature reaches a predetermined upper limit.

The present invention relates to an improvement of the glow plug energization control device of the above type as exemplified in Japanese Patent Application Laid-Open No. 57-2471, and maintains the glow plug temperature by taking into account changes in the battery voltage applied to the glow plug. The purpose is to do something.

That is, the present invention changes the voltage that is intermittently applied to the glow plug during intermittent energization into a first signal proportional to the square of the voltage during energization, and converts this squared first signal into a direct current. is averaged to obtain a second signal, and this averaged second signal is compared with a third value corresponding to a constant comparison voltage independent of the power supply voltage. If the signal is smaller than the signal, the glow plug is energized, and if it is larger than the signal, the energization is stopped.By doing so, the effective voltage applied to the glow plug is maintained constant regardless of changes in the power supply voltage. It is characterized by

To explain the illustrated embodiment, in Fig. 1 shown as a block diagram (2) and an electrical wiring diagram showing its details, 1 is a battery, 2 is a key switch, and 3 is a key switch that responds to the power supply voltage after opening. 7 is a three-terminal regulator, 11 is a driver circuit, 13 is a plug energization circuit that opens and closes the voltage application to the glow plug; Install it near. (in Figure 2) 14
．． 15 is a transistor constituting the glow plug energizing circuit 13; 16a, 16b, 16c, and 16d are four glow plugs connected in parallel; 19 is a voltage 2 that produces a voltage proportional to the square of the voltage applied to the glow plugs; multiplication circuit,
20 is an average voltage generation circuit that converts intermittent voltage into an average DC voltage, 21 is a constant voltage circuit that divides the constant voltage of the 3-terminal regulator to create another constant voltage by resistance, 22 is a comparator, and 23 is the output of comparator 22. 33 is a timer circuit for afterglow, and 34 is a circuit package for the energization control device.

(3) In FIG. 2, when the key switch 2 is opened, the rapid heating timer circuit 3 receives the output voltage (for example, 5 V) of the output cuff a of the three-terminal regulator 7 through the resistor 8.9. Whereas it is a divided voltage (e.g. 4V),
- Example input: Since the voltage of the capacitor 5 is initially Ov, the output of the comparator 4 becomes a high level, and the driver circuit 11 is energized via the pull-up resistor 10. The output 12 of the driver circuit 11 is connected to the plug energizing circuit 1.
It works to turn on transistors 14 and 15 of No. 3,
Battery voltage is applied to the glow plugs 16a to 16d, and rapid heating is started.

As a result, the voltage at the + side terminal 17 of the glow plug 16 is
The capacitor 5 is charged via the charging time constant circuit 6. This charging time constant circuit 6 has nonlinearity. The time it takes for the voltage of the capacitor 5 to reach the + side input voltage of the comparator 4 is determined by the glow plugs 16a to 16.
Since the time for the temperature of d to reach a predetermined upper limit temperature (for example, 900 degrees Celsius) is set to match the time, when the voltage of the capacitor 5 reaches the reference voltage (4V) of the comparator 4, the output of the comparator 4 becomes low level, and driver circuit 1
1 becomes deenergized, and the plug energizing circuit 13 also becomes non-conductive.
The voltage at the + side terminals 17 of the glow plugs 16a to 16d once becomes Ov.

Note that when the output of comparator 4 becomes low level, the + side input terminal of comparator 4 becomes almost low level through No. 18, so the output of comparator 4 will remain low level from then on until the key switch is turned OFF. keep.

Now, once the glow plug applied voltage becomes 0■, after that, it is controlled at a constant frequency of, for example, 10Hz to 100Hz by the voltage square circuit 19, average voltage generation circuit 20, constant voltage circuit 21, comparator 22, and delay circuit 23. , the battery voltage is energized intermittently so that the rated effective voltage is applied to the glow plugs 168 to 16d. When the rapid heating timer circuit 3 is operating, that is, when the battery voltage is being applied to the glow plugs 16a to 16d in a DC manner, the capacitor 24 (for example, 10 μF) in the average voltage generating circuit 20 (5) ) is resistance 25°26
DC voltage (for example, battery voltage 1
The capacitor 24. was charged to 3.55V, which is 1/2 of 7.1V when the voltage was 2V, but from the moment the glow plug voltage became Ov, the capacitor 24. It discharges at a time constant determined by a resistor of 5°26. On the other hand, the + side input voltage of the comparator 22 is the voltage at the output cuff a of the three-terminal regulator at the resistor 28.
For example, when the voltage of the capacitor 24 drops to 1.5V, the output of the comparator 22, which was previously at a low level, is inverted to a high level. This high level passes through the delay circuit 23 and energizes the driver circuit 11 after about 10 m5, so that the plug energizing circuit 13 becomes conductive and the glow plug 16
The battery voltage is again applied to a3 16d.

However, as a result of this voltage application, the voltage of the capacitor 24 returns to the output of the constant voltage circuit 21, that is, the positive input terminals 1 and 5B of the comparator (6) 22, in a very short time (1 ms or less) via the resistor 25. The output of 22 is again at a low level, and the voltage application to the glow plug is turned off. This is 100 Hz
By repeating this at a certain frequency, the plug energizing circuit 11 repeats intermittent operation at a duty ratio such that the voltage of the capacitor 24 becomes equal to the constant voltage of the constant voltage generating circuit 29.

Now, to describe the functions of the voltage square circuit 19 and the average voltage generation circuit, when performing intermittent square wave energization, the power PON during energization is proportional to the square of the voltage VON at the time of energization. In order to make the average power for one cycle constant even if VON changes, that is, to make the effective voltage applied to the glow plug constant, a voltage proportional to the square of VON is applied intermittently. What is necessary is to take the average of the time for the period and make this average value Vm constant without depending on VON.

In the case of this embodiment, the voltage square circuit 19 is constituted by a simple circuit consisting of a Zener diode 30 and a resistor 31. The Zener diode is, for example, an RD5-IE made by Nippon Electric Co., Ltd., and the resistor is IKΩ. A characteristic as shown in FIG. 3 fbl is obtained. The output voltage when the power supply voltage is 12V in FIG. 3 (al is in FIG. 3) is 7.
It is a true square curve passing through the point 1■, but when the power supply voltage is 8V~
Between 12V, (al and (bl) almost match, and at a power supply voltage of 16V, the ideal value is 12.6V, but the actual value is 10.IV and the difference is somewhat large.

When the effective voltage applied to the glow plug at the angular power supply voltage applied to the glow plug is determined as shown in FIG. 3 (when the target effective voltage is controlled to 6V by the circuit in FIG. If the effective voltage is V R%, the applied voltage is Vp, and the energization rate during ON and OFF intermittent energization is d, then there is a relationship of vR = ψVp' In this case, if vR-52'xd=6V, then d=0.25.

The conduction rate when the power supply voltage is 8V and 12V is based on the condition that the time average of the output voltage of the voltage square circuit is equal for all square power supply voltages. 25 vs. 0.
It is determined by 25X (Vp when the power supply voltage is 12V)/(Vp at each power supply voltage).

As a result, the conduction rate d8 when the power supply voltage is 8V is d e
=0.25X (T, IV) / (3,23V
l = 0.55 The conduction rate d16 when the power supply voltage is 16V is
d + s = 0.25X (7,1ν) / (1
1,OV) = 0.161, and these dllll
Using d16 to find the effective voltage ■R, the effective voltage VR8 when the power supply voltage is 8V is vR8 Yes, 1st layer T -5,93
V The effective voltage VR16 when the power supply voltage is 16V is VR+6=
F11-5 "Ti is -6,42V, and when these are illustrated, it becomes as shown in Figure 4 (b), and it is a downwardly convex arc shape with the ideal characteristic in Figure 4 (al is constant 6V) However, when the power supply voltage is in the practical range of 8 to 16 V, a substantially constant effective voltage is obtained, and the glow plug temperature is maintained at a substantially constant temperature regardless of the power supply voltage.

The time period during which the glow plug continues to maintain the darkening temperature is determined by, for example, the output 33 of the afterglow timer circuit 32 that operates from the time when the key switch 2 is closed (9).
continues while the glow plug is open, and after a predetermined afterglow hour has elapsed, the output 33 becomes a low level, forcibly deactivating the driver circuit 11 and ending the glow plug energization. In addition,
The afterglow timer circuit 11 can be controlled in time by a signal from a water temperature sensor (not shown), or can be operated until the water temperature rises to a predetermined value.

In the embodiments described above, the timer circuit 3 is used as the rapid heating means, but other timer means may also be used. It can also be used in a device that detects an increase in temperature. In some cases, the intermittent energization method of the present invention may be used from the beginning without particularly performing rapid heating. Further, in this embodiment, a transistor current amplifying circuit is used as the plug energizing circuit, but other switching devices such as a cylindrical circuit, a gate turn-off cylindrical circuit, or an electromagnetic relay may be used.

Further, in this embodiment, an approximate square circuit consisting of a Tse(10)ner diode 30 and a resistor 31 is used as the square voltage generating circuit, but the output voltage is proportional to the square of the input voltage or approximately square Any circuit may be used as long as it has close to the multiplicative characteristic. Furthermore, when the present device is configured using a microcomputer, the voltage applied to the glow plug can be taken in as a digital value, the value can be squared or calculated, and further averaging can be performed by digital processing.

As described above, according to the present invention, the effective voltage applied to the glow plug can be maintained even when the power supply voltage fluctuates, the heating effect can be exerted even during cranking, and the plug can be prevented from being overpowered. There is no.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is an electrical wiring diagram showing details of Fig. 1, and Figs. 3 and 4 are characteristic diagrams for explaining the operation of the embodiment. be. 11... Driver circuit, 13... Energizing circuit, 19.
...Voltage squared, 20...Average voltage generation circuit,
21... Constant voltage circuit, 22... Comparator for comparison. Representative Patent Attorney Takashi Okabe

Claims (1)

[Claims] A glow plug energization method in which a power supply voltage higher than the rated voltage is applied, and after the voltage reaches a predetermined upper limit temperature near a predetermined upper limit temperature, the voltage is switched to intermittent energization with an energization rate according to the power supply voltage to perform stable heating. In the control method, the voltage that is intermittently applied to the plug is converted into a first signal proportional to the square of the voltage when the plug is energized, and the squared first signal is DC averaged to generate a second signal. signal, and this averaged second signal is used as a third signal corresponding to a constant comparison voltage that does not depend on the power supply voltage.
, and if the second signal is smaller than the third signal, the glow plug is energized, and if the second signal is larger than the third signal, the glow plug is energized and stopped.